To assist in understanding the context of the Invention, a conventional insulation terminal and a method for producing the same will be described below by referring to FIGS. 3 and 4.
Automobiles are equipped with electronic units for controlling various devices such as electronic fuel injection systems, antilock brakes, and the like. These units can be placed in the passenger compartment or the engine compartment. In the former case, as shown in FIG. 3, control unit 1 is disposed in passenger compartment 2a of automobile 2. Wire harness W/H must pass from engine compartment 2b to passenger compartment 2a. Not only would this require wire harness W/H to be long, it also necessitates an opening in panel 2c which separates the passenger compartment from the engine compartment. This requires complex operations and increases costs.
On the other hand, if the control unit is located in the engine compartment, it is exposed to water which can enter the compartment and thereby damage the unit. Moreover, the heat generated by the engine also presents a serious problem. These units contain semi-conductors which do not have adequate heat resistance. In order to obtain such resistance, special semi-conductors must be used. This also increases the cost.
Another solution for protecting the electronic control units has been suggested in Japanese Patent Application number 7-321584. In this Application, a storage box protects the electronic control units and is disposed in the engine room. As shown in FIG. 4, electronic control unit 1 is stored in inner box 3 which, in turn, is stored in outer box 4. Outer box 4 is sealed with cover 5. Spaces 5A and 5B are formed between inner box 3 and outer box 4 to allow cool air to circulate between the two boxes and prevent overheating. Inner box 3 is watertight due to a seal at opening 3a. Since inner box 3 is watertight, it prevents water from entering the inside of inner box 3 and damaging the electronic control units.
Heat is generated by the electronic control units which, in turn, increases the temperature inside inner box 3. It has also been found that, with the storage box shown in FIG. 4, the temperature in spaces 5A and 5B is lower than the temperature inside inner box 3. This difference in temperature results in a negative pressure because air tries to flow from the inside of inner box 3 into spaces 5A and 5B, but is prevented from doing so because inner box 3 is watertight. This negative pressure causes the inner box to deform, which, in turn, creates a gap that allows water and dirt to enter.